1. Field
The present invention relates to turbine vanes and blades for a gas turbine stage and, more particularly, to third and fourth stage turbine vane and blade airfoil configurations.
2. Description of the Related Art
In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor then mixed with fuel and burned in a combustor to generate hot combustion gases. The hot combustion gases are expanded within the turbine section where energy is extracted to power the compressor and to produce useful work, such as turning a generator to produce electricity. The hot combustion gas travels through a series of turbine stages. A turbine stage may include a row of stationary vanes followed by a row of rotating turbine blades, where the turbine blades extract energy from the hot combustion gas for powering the compressor, and may additionally provide an output power.
The overall work output from the turbine is distributed into all of the stages. The stationary vanes are provided to accelerate the flow and turn the flow to feed into the downstream rotating blades to generate torque to drive the upstream compressor. The flow turning in each rotating blade creates a reaction force on the blade to produce the torque. The work transformation from the gas flow to the rotor disk is directly related to the engine efficiency, and the distribution of the work split for each stage and the associated airfoil angles may be controlled by the vane and blade design for each stage and studied and selected for each unique engine design. Each row of airfoils has a unique set of inlet angles at the airfoil leading edge and a set of exit angles at the airfoil trailing edge. These angles are varied along the radial direction from the root to the tip.